FFT Spectrum Analyzers

Transcription

1 FFT Spectrum Analyzers SR khz two-channel dynamic signal analyzer SR780 Dynamic Signal Analyzer DC to khz bandwidth 90 db dynamic range Low-distortion synthesized source 145 db dynamic range in swept-sine mode Real-time octave analysis Up to 32 Mbyte memory GPIB and RS-232 interfaces The SR780 Dynamic Signal Analyzer combines high performance and low cost in a full-featured package. It offers khz FFTs with 90 db dynamic range, sweptsine measurements, ANSI standard octave analysis, waterfall displays, and transient capture for less than half the cost of other similarly equipped analyzers. Spectrum Analysis The SR780 delivers true two-channel, khz FFT performance. Its fast 32-bit floating-point DSP processor gives the SR780 a khz real-time rate with both channels selected. Two precision 16-bit ADCs provide a 90 db dynamic range in FFT mode. Selectable 100 to 800 line analysis optimizes time and frequency resolution, and you can zoom in on any portion of the khz range with a frequency span down to 191 mhz. The SR780 s unique architecture lets the two displays function independently. You can choose separate frequency spans, starting frequencies, number of FFT lines, or averaging modes for each display. So it s easy to look at a wideband display and zoom in on a specific feature simultaneously. The SR780 lets you select from two sampling rates: 256 khz or 262 khz, so frequency spans come out in either a binary (102.4 khz, 51.2 khz,...) or decimal (100 khz, 50 khz, 25 khz,...) sequence depending on your requirements. SR $9950 (U.S. list) Stanford Research Systems phone: (408)

2 SR780 Dynamic Signal Analyzer Octave analysis is fully compliant with ANSI and IEC standards. Full octave, 1/3 octave and 1/12 octave analysis are all available. Switchable analog A-weighting filters, as well as built-in user math weighting functions (A, B and C), are included. Octave averaging choices include exponential time averaging, linear time averaging, peak hold, and equal confidence averaging. IEC compliant peak hold, impulse, fast and slow sound level measurements are all calculated. Swept-Sine Analysis Swept-sine analysis is used for measurements involving high dynamic range or wide frequency intervals, and is also Narrow band FFT (top), wideband FFT (bottom) Flexible Averaging Several averaging choices are provided. RMS averaging reduces signal fluctuations, while vector averaging minimizes noise from synchronous signals. You can choose linear averaging (stable averaging) for fixed signals, or exponential averaging to track drifting features. Because the SR780 s khz real-time bandwidth lets it take data seamlessly, vector averaging can be selected for any signal that s repetitive within the time record no trigger is necessary. Transducer Units Automatic unit conversion makes translating accelerometer data easy. You can enter your accelerometer conversions directly in V/EU, EU/V or db (1 V/EU). The SR780 will display results in units of meters, inches, mil, g, kg, lbs., N, dynes, pascals, bars or dbspl. Accelerometer data is automatically converted to velocity or displacement units. Built-in ICP power means you won t need an external power supply for your accelerometer. Swept-sine Bode plot of low-pass filter response a standard feature of the SR780. Selectable auto-ranging optimizes the input range at each point in the measurement, providing up to 145 db of dynamic range. Auto-ranging can be used with source auto-leveling to maintain a constant input or output level at the device under test. To ensure the fastest sweeps possible, auto-resolution can also be selected, providing a variable scan speed tailored precisely to the signal being measured. User Math User-defined math functions are available in all measurement groups. Equations are created from time or frequency data, Octave analysis Octave Analysis Real-time octave analysis, at frequencies up to 40 khz (single channel) or 20 khz (dual channel), is standard in the SR780. User math Stanford Research Systems phone: (408)

3 SR780 Dynamic Signal Analyzer stored files, constants, or a rich array of supplied operations including the arithmetic functions, FFT, inverse FFT, jω, d/dω, exp, ln x and many others. Unlike many analyzers, the SR780 s measurement rate isn t reduced when user math is selected. For instance, the function exp(ln(conj(avg(fft2/ FFT1))) can be calculated with a 50 khz real-time bandwidth. Source Six source types are available: low distortion ( 80 dbc) single or two-tone sine waves, chirp, white noise, pink noise and arbitrary waveforms. The chirp and noise sources can both be bursted to provide a source that s active only over a selected portion of the time record for FFT measurements, or to provide an impulsive noise source for acoustic measurements. The digitally synthesized source provides output levels from 0.1 mv to 5 V, and delivers up to 100 ma of current. Arbitrary waveform capability is standard on the SR780. The arbitrary source can be used to playback a section of a captured waveform, play a selected FFT time record, or upload a custom waveform. Capture The SR780 comes standard with 2 Msamples of capture memory. Waveforms can be captured at 262 khz or any submultiple of 262 khz, allowing you to select the sample rate and capture length that s right for your data. Once captured, any portion of the signal can be played back in FFT or Octave mode. The convenient AutoPan feature lets you display the measurement results synchronously with the corresponding portion of the capture buffer to easily identify important features. An optional memory expansion module lets you extend the SR780 s capture depth to 8 Msamples that s almost 30 seconds of capture at the maximum sampling rate. octave measurements. While displaying waterfalls, you can adjust the skew angle to reveal important features, or change the baseline threshold to eliminate low-level clutter. Any z-axis slice or x-axis record can be saved to disk or displayed separately for individual analysis. Analysis The SR780 includes a wide variety of analysis features. Marker analysis lets you use the marker to measure the power contained in the harmonics, sidebands or within a given band of frequencies. THD, THD + N, sideband power relative to carrier, and total integrated power are calculated in real time and displayed on the screen. Marker statistics quickly calculate the maximum, minimum, mean and standard deviation of data at any point in the display. A data table feature lets you display up to 100 selected data points in tabular format. Limit tables let you to define up to 100 upper and lower limit segments in each display for GO/ NO-GO testing. Output The SR780 s 3.5" disk drive, computer interfaces (GPIB and RS-232) and printer port provide flexibility when saving, printing and exporting data. Data can be saved in binary or ASCII formats, and displays can be printed/plotted to any of the ports or the disk drive. Supported formats include PCL (LaserJet/DeskJet), dot-matrix, postscript, HP-GL, PCX or GIF. Utilities are included to translate HP SDF files into SR780 format. Waterfall All Octave and FFT measurements can be stored in the SR780 s 2k-deep waterfall buffers. Waterfall storage is selectable as every n th time record for FFT measurements, or you can select a storage interval in seconds (down to 4 ms) for Waterfall plot Stanford Research Systems phone: (408)

4 SR780 Features FFT Measurement Group FFT, Time Record, Windowed Time, Time Capture, Transfer Function, Cross Spectrum, Coherence, Cross-Correlation, Auto-Correlation, Orbit, User Math Octave Analysis Measurement Group 1/1, 1/3, 1/12 Octave, Time Capture, User Math, L eq, Impulse, Total Power Swept-Sine Measurement Group Spectrum, Transfer Function, Cross Spectrum, User Math FFT Resolution 100, 200, 400, 800 lines Views Linear Magnitude, Log Magnitude, Magnitude Squared, Real Part, Imaginary Part, Phase, Unwrapped Phase, Nichols, Nyquist Units V, V 2, V 2 /Hz, V/ Hz, meters, inches, mils, g, kg, lbs., N, dynes, pascals, bars, SPL, user-defined engineering units Displays Single, Dual, Waterfall with Skew, Zoom and Pan Averaging RMS, Vector, Peak Hold, Linear, Exponential, Equal Confidence (Octave), Preview Time Record Triggering Continuous, Internal, External (Analog or TTL), Source, Auto/Manual Arming Source Outputs Sine, Two-Tone, Swept-Sine, White/Pink Noise, Burst Noise, Chirp, Burst Chirp, and Arbitrary Windows Hanning, Blackman-Harris, Flat-Top, Kaiser, Force/ Exponential, User-Defined, ±T/2, ±T/4, T/2, Uniform User Math +,,,, Conjugate, Magnitude/Phase, Real/Imaginary, Sqrt, FFT, Inverse FFT, jω, Log, Exp, d/dx, Group Delay, A-Weighting, B-Weighting, C-Weighting, x/x 1 Analysis Harmonic, Band, Sideband, THD, THD + N, Limit Test, Data Table, Exceedance, Statistics Time Capture Captures time data for later analysis (FFT or Octave). Up to 2 Msamples (8 Msamples opt.) of data can be saved. Storage 3.5", 1.44 Mbyte, DOS formatted disk Hard Copy and Interfaces Print to dot-matrix or PCL (LaserJet and DeskJet) printers. Plot to HP-GL or postscript plotters. Print/plot on-line (RS- 232 serial, Centronics parallel or IEEE-488.2) or to disk file. EPS, GIF, PCX graphic formats also available for disk storage. Help Full, context-sensitive help screens for all SR780 features mean you will rarely have to refer to a printed manual. Hypertext links let you quickly switch between related help pages or instantly reference the remote command corresponding to any SR780 function. Use the help index to quickly locate help on any topic, jump to the online troubleshooting guide, browse a complete listing of the SR780 s specifications, or examine a comprehensive description the SR780 s remote commands. Ordering Information SR780 Dynamic signal analyzer $9950 O780M1 8 Msample (32 Mbyte) memory $800 O780RM Rack mount kit $100 CT100 SRS instrument cart $850 SR780 rear panel Stanford Research Systems phone: (408)

5 SR780 Specifications Specifications apply after 30 minutes warm-up and within two hours of last auto-offset. Measured with 400-line resolution and anti-alias filters enabled unless stated otherwise. Measurement Groups Group Frequency FFT, Octave Analysis, Swept-Sine Range khz or 100 khz (both displays have the same range) FFT spans mhz to khz or 191 mhz to 100 khz. The two displays can have different spans and start frequencies. FFT resolution 100, 200, 400 or 800 lines Real-time bandwidth khz (highest FFT span with continuous data acquisition and averaging) Accuracy 25 ppm from 20 C to 40 C Dynamic Range Dynamic range FFT and Octave Swept-Sine Harmonic distortion Intermodulation dist. Spurious Alias responses Full-span FFT noise floor Residual DC response 90 db typical, 80 db guaranteed 145 db Includes spurs, harmonic and intermodulation distortion and alias products. Excludes alias responses at extremes of span. < 80 db (single tone in band) < 80 db (two tones in band, each less than 6.02 dbfs) < 80 dbfs < 80 dbfs (single tone outside of span, <0 dbfs, <1 MHz) 100 dbfs typical (input grounded, range > 30 dbv, Hanning window, 64 rms averages) < 30 dbfs (FFT with Auto-Cal on) Cross channel Signal Inputs Flattop and Kaiser windows, phase is relative to a cosine wave at the center of the time record. For Uniform, Force and Exponential windows, phase is relative to a cosine wave at the beginning of the time record. ±0.5 deg. (DC to 51.2 khz) ±1.0 deg. (DC to khz) (transfer function measurement, both inputs on the same input range, vector averaged) Number of inputs 2 Full-scale input range 50 dbv (3.16 mvp) to +34 dbv (50 Vp) in 2 db steps Maximum input level 57 Vp Input configuration Single-ended (A), differential (A B) Input impedance 1 MΩ + 50 pf Shield to chassis Floating mode: 1 MΩ µf Grounded mode: 50 Ω Shields are always grounded in differential input (A B) Max. shield voltage 4 Vp AC coupling 0.16 Hz cutoff frequency CMRR 90 db at 1 khz (input range <0 dbv) 80 db at 1 khz (input range <10 dbv) 50 db at 1 khz (input range 10 dbv) ICP signal Current source: 4.8 ma Open circuit voltage: +26 V A-weight filter Type 0 tolerance, ANSI standard S (10 Hz to 25.6 khz) Crosstalk < 145 db below signal (input to input and source to inputs, 50 Ω receiving input source impedance) Input noise <10 nvrms/ Hz above 200 Hz (< 160 dbvrms/ Hz) Trigger Input Amplitude Accuracy Single channel Cross channel Phase Accuracy Single channel ±0.2 db (excluding windowing) ±0.05 db (DC to khz) (transfer function meas., both inputs on same range, rms averaged) ±3.0 deg. relative to external TTL trigger ( 50 dbfs to 0 dbfs, frequency <10.24 khz, center of frequency bin, DC coupled). For Blackman-Harris, Hanning, Modes Internal External External TTL Post-trigger Free Run, Internal, External, or External TTL Level adjustable to ±100 % of input scale. Positive or negative slope. Min. trigger level: 5 % of input range Level adjustable to ±5 V in 40 mv steps. Positive or negative slope. Input impedance: 1 MΩ Max. input: ±5 V Min. trigger level: 100 mv Requires TTL level to trigger (low <0.7 V, high >3.0 V) Measurement record is delayed up to 8192 samples after the trigger. Stanford Research Systems phone: (408)

6 SR780 Specifications Pre-trigger Measurement record starts up to 8192 samples prior to the trigger. Flatness <0.25 dbpp (typ.), <1.0 dbpp (max.), 5000 rms averages Transient Capture Pink Noise Source Mode Maximum rate Max. capture length Octave Analysis Standards Frequency range Accuracy Dynamic range Sound level Continuous data recording 262,144 samples/s for both inputs 2 Msamples (single input) 8 Msamples with optional memory Conforms to ANSI std. S Order 3 Type 1-D and IEC Single channel: 1/1 Octave Hz to 32 khz 1/3 Octave Hz to 40 khz 1/12 Octave Hz to 12.3 khz Two channels: 1/1 Octave Hz to 16 khz 1/3 Octave Hz to 20 khz 1/12 Octave Hz to 6.17 khz <0.2 B (1 second stable average, single tone at band center) 80 db (1/3 octave, 2 second stable average) per ANSI S Impulse, Peak, Fast, Slow and L eq per ANSI S Type 0 and IEC Type 0 Bandwidth Flatness Chirp Source Time record Output Flatness Swept-Sine Source Auto functions Dynamic range Arbitrary Source Amplitude range Record length General DC to khz <2.0 dbpp, 20 Hz to 20 khz (using averaged 1/3 octave analysis) Continuous or burst Sine sweep across the FFT span ±0.25 dbpp (amplitude: 1.0 Vp) Source level, input range and frequency resolution 145 db ±5 V 2 Msamples (playback from arbitrary waveform memory or capture buffer), variable sample rate Source Output Amplitude range Amplitude resolution DC offset Offset adjust Output impedance Sine Source Amplitude accuracy Harmonics, sub-harm. & spurious Two-Tone Source Amplitude accuracy Harmonics, sub-harm. White Noise Source 0.1 mvp to 5 Vp 0.1 mvp (output >500 mvp) <10.0 mv (typ.) ±5 VDC (sine, two-tone) <5 Ω, ±100 ma peak output current ±1 % of setting, 0 Hz to khz, 0.1 Vp to 5.0 Vp, Hi-Z load 0.1 Vp to 5 Vp < 80 Bc (fundamental <30 khz) < 75 dbc (fundamental <102 khz) ±1 % of setting, 0 Hz to khz, 0.1 Vp to 5 Vp, Hi-Z load < 80 dbc, 0.1 Vp to 2.5 Vp CRT monitor Interfaces Hardcopy Disk drive Preamp Power Power Dimensions Weight Warranty Monochrome, 800H 600V resolution IEEE-488.2, RS-232 and printer interfaces standard. All instrument functions can be controlled through the computer interfaces. A PC (XT) keyboard input is provided for additional flexibility. Print to dot matrix and PCL compatible printers. Plot to HP-GL or postscript plotters. Print/Plot to RS-232 or IEEE interfaces or to disk file. Additional file formats include GIF, PCX and EPS. 3.5" DOS format, 1.44 MB. Storage of displays, setups and hardcopy. Power connector for SRS preamps 70 W, 100/120/220/240 VAC, 50/60 Hz 17" 8.25" 24" (WHD) 56 lbs. One year parts and labor on defects in materials and workmanship Time Record Bandwidth Continuous or burst DC to khz or limited to span Stanford Research Systems phone: (408)